WO2008001657A1 - Fluid pressure drive device - Google Patents

Abstract

A fluid pressure drive device having a small inexpensive structure and achieving both control of high pressure and control of a large flow rate at the same time. Tandem hydraulic pumps that are a first fixed displacement hydraulic pump (1) with a medium displacement and a second fixed displacement hydraulic pump (2) with a small displacement are driven by a servo motor (3). Hydraulic oil from the first and second fixed displacement hydraulic pumps (1, 2) is controlled by a four-port three-position type electromagnetic switchover valve (5). The electromagnetic switchover valve (5) has a first position (S1) at which first and second input ports (P1, P2) are communicated with an output port (A) and a return port (R) is closed, a second position (S2) at which the first input port (P1) is communicated with the output port (A) and the second input port (P1) is communicated with the return port (R), and a third position (S3) at which the first input port (P1) is communicated with the return port (R) and the second input port (P2) is communicated with the output port (A).

Description

 Specification

 Hydraulic drive device

 Technical field

 [0001] The present invention relates to a hydraulic drive apparatus suitable for use in, for example, an injection molding machine, a machine tool, a construction machine, and the like.

 Background art

 Conventionally, as a hydraulic drive device, one fixed displacement hydraulic pump is driven by a servo motor, and a controller is used based on a pressure detection value, a flow detection value, a pressure command value, and a flow command value. Some servo motors are controlled (Japanese Patent Publication No. 2000-320466).

 [0003] By the way, in the conventional hydraulic drive apparatus, since one fixed displacement hydraulic pump is driven by a servo motor, the shaft torque required for the servo motor is the load pressure and the fixed displacement hydraulic pump. It will be proportional to the capacity of the pump. For this reason, when a large capacity fixed displacement hydraulic pump is used when a large flow rate is required, if the load pressure increases, the required shaft torque and drive current of the servo motor will become extremely large. Bo-motors and controllers become very large and expensive.

 [0004] On the other hand, when high pressure is required, using a small-capacity fixed displacement hydraulic pump to reduce the shaft torque required by the servo motor will meet that requirement when a large flow rate is required. I can't.

 [0005] As described above, the above-described conventional hydraulic drive device has a problem in that it cannot achieve both high pressure control and large flow rate control with a small and inexpensive structure.

 Disclosure of the invention

 Problems to be solved by the invention

[0006] Accordingly, an object of the present invention is to provide a hydraulic drive device that can achieve both high pressure control and large flow rate control with a small and inexpensive structure.

 Means for solving the problem

[0007] In order to solve the above problems, a hydraulic drive device of the present invention includes: Two medium-capacity first fixed displacement hydraulic pumps whose shafts are connected to each other, and a second fixed displacement hydraulic pump having a small capacity smaller than the above-mentioned medium capacity;

 A first input port connected to the discharge port of the first fixed displacement hydraulic pump, a second input port connected to the discharge port of the second fixed displacement hydraulic pump, and a load line. A first position in which the first and second input ports communicate with the output port, while the return port is closed, and the first input. The port communicates with the output port while the second input port communicates with the return port, and the second input port communicates with the return port while the second input port communicates with the output port. A four-port three-position electromagnetic switching valve having a third position, a servo motor for driving the first fixed displacement hydraulic pump and the second fixed displacement hydraulic pump,

 A pressure sensor for directly or indirectly detecting the pressure of the load line;

 The flow line detection sensor that detects the rotational position or speed of the servo motor, the outputs of the pressure sensor and the flow rate detection sensor, and the pressure command and flow rate command receive the pressure and flow rate of the load line. And a controller for controlling the servo motor so that the pressure and flow rate correspond to the pressure command and flow rate command.

[0008] According to the hydraulic drive apparatus having the above-described configuration, the controller positions the 4-port 3-position electromagnetic switching valve at the first position when controlling a low pressure and a large flow rate.

[0009] Then, the medium flow rate liquid flowing from the medium capacity first fixed displacement hydraulic pump into the first input port of the electromagnetic switching valve and the small capacity second fixed displacement hydraulic pump force electromagnetic A small amount of liquid flowing into the second input port of the switching valve merges, and a large amount of liquid is supplied from the output port to the load line.

At this time, the controller controls the load line pressure and flow rate based on a pressure command indicating a low pressure, a flow rate command indicating a large flow rate, a signal from a pressure sensor, and a signal from a flow rate detection sensor. The rotational speed of the servo motor is controlled so that is at the low pressure and large flow rate.

[0011] Thus, when the electromagnetic switching valve is located at the first position, To control low pressure and large flow rate.

 On the other hand, at the time of controlling the medium pressure / medium flow rate, the controller positions the electromagnetic switching valve at the second position.

 [0013] Then, a small flow amount of liquid flowing into the second input port of the electromagnetic switching valve from the small-capacity second fixed displacement hydraulic pump is discharged from the return port to the tank, and the second fixed displacement The hydraulic pump is unloaded. However, the medium flow rate liquid flowing into the first input port of the electromagnetic switching valve from the first fixed displacement hydraulic pump is supplied from the output port to the load line.

 At this time, the controller controls the load line pressure and the pressure based on the pressure command indicating the intermediate pressure, the flow rate command indicating the intermediate flow rate, the signal from the pressure sensor, and the signal from the flow rate detection sensor. The rotational speed of the servo motor is controlled so that the flow rate becomes the medium pressure and medium flow rate.

 [0015] As described above, when the electromagnetic switching valve is located at the second position, the medium pressure flow is controlled with respect to the load line.

[0016] Further, at the time of controlling the high pressure and the small flow rate, the controller positions the electromagnetic switching valve at a third position.

 [0017] Then, the medium flow rate liquid flowing from the medium capacity first fixed displacement hydraulic pump into the first input port of the electromagnetic switching valve is discharged from the return port to the tank, and the first fixed displacement The hydraulic pump is unloaded. However, a small amount of liquid flowing from the second fixed displacement hydraulic pump to the second input port of the electromagnetic switching valve is supplied from the output port to the load line.

 [0018] At this time, the controller controls the pressure and flow rate of the load line based on the pressure command indicating high pressure, the flow rate command indicating small flow rate, the signal from the pressure sensor, and the signal from the flow rate detection sensor. The rotational speed of the servo motor is controlled so that is at the high pressure and small flow rate.

 As described above, when the electromagnetic switching valve is located at the third position, the high pressure and small flow rate is controlled with respect to the load line.

[0020] Thus, only one 4-port 3-position electromagnetic switching valve and the above-described connection structure are used. Therefore, it is possible to reduce the shaft torque required for the servo motor by selecting three stages of operation modes: low pressure, large flow, medium pressure, medium flow, and high pressure, small flow.

[0021] Therefore, according to the present invention, it is possible to achieve both high pressure control and large flow rate control, and the current value required by the servo motor and controller can be reduced, making the servo motor and controller small and inexpensive. Can be.

[0022] Further, for example, in a hydraulic drive device of an injection molding machine or a press machine, there has been a request to maintain a high pressure for a long time. Conventionally, a servo motor or a controller generates heat due to a large current. There was a problem that this request could not be met because of the increase in size. However, in the hydraulic pressure driving device having the above configuration, the current value force becomes small, and therefore, the pressure can be maintained for a long time at a high pressure.

[0023] In one embodiment, a hydraulic drive device comprises:

 The flow toward the load line is forward between the discharge port of the first fixed displacement hydraulic pump and the first input port of the electromagnetic switching valve and the load line. A connected first check valve;

 The flow toward the load line is forward between the discharge port of the second fixed displacement hydraulic pump and the second input port of the electromagnetic switching valve and the load line. With a connected second check valve

 Is provided.

 [0024] According to the above embodiment, it is assumed that the electromagnetic switching valve is locked with, for example, dust and the like, between the first position and the second position, or between the first position and the third position. Even if the first input port, the second input port, and the output port are closed, the liquid from the first and second fixed displacement hydraulic pumps is allowed to flow through the electromagnetic switching valve. Can be supplied to the load line through the first check valve and the second check valve. In this way, when the electromagnetic switching valve fails, the electromagnetic switching valve is bypassed by the first check valve and the second check valve, so that the piping and hydraulic equipment can be prevented from being damaged.

 [0025] In addition, the hydraulic drive device of one embodiment includes:

 A relief valve connected to the load line;

[0026] According to the embodiment, the first and second check valves are controlled by the relief valve. Even if the pressure in the load line is excessive due to the liquid supplied from the liquid, the liquid can be released to the tank to prevent the pressure from becoming excessive, and damage to the equipment can be prevented.

 [0027] Further, in the hydraulic drive device of one embodiment,

 The above controller

 A pressure control unit that receives the pressure command and a pressure detection signal of the pressure sensor force and outputs a pressure control signal based on a deviation between the pressure command and the pressure detection signal; and a pressure control from the pressure control unit A limiting unit that receives a signal and a flow rate command and outputs a limit control signal generated by adding a limit corresponding to the flow rate command to the pressure control signal; a limit control signal for the limit unit force; and the flow rate detection sensor Based on the force flow rate detection signal, a rotation speed control signal is generated to control the load line pressure and flow rate so that the pressure and flow rate correspond to the pressure command and flow rate command. Rotation speed controller that outputs to the motor

 Is provided.

 [0028] According to the embodiment, the restriction unit adds a restriction corresponding to the flow rate command to the pressure control signal based on the deviation between the pressure command and the pressure detection signal, as well as being output from the pressure control unit. A limit control signal is generated (with limiter control). Based on the restriction control signal and the flow rate detection signal from the flow rate detection sensor, the rotation speed control unit converts the pressure and flow rate of the load line to the pressure command and the flow rate according to the pressure command and the flow rate command. A rotation speed control signal is generated for control so as to be and output to the servo motor.

 [0029] In this way, a restriction control signal is created by adding a restriction according to the flow rate command to the pressure control signal by the restriction unit, and the pressure and the flow rate are controlled based on the restriction control signal. Pressure control and flow rate control can be performed accurately and smoothly.

 The invention's effect

 [0030] According to the present invention, there is provided a hydraulic drive device that can achieve both high-pressure control and high-flow rate control with a small and inexpensive structure, with a small motor shaft torque and controller output current. be able to.

Brief Description of Drawings FIG. 1 is a circuit diagram of a hydraulic driving apparatus according to one embodiment of the present invention.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.

 [0033] As shown in FIG. 1, this hydraulic drive device includes two first fixed-capacity hydraulic pumps 1 and second fixed-capacity hydraulic pumps 2 whose shafts are connected to each other. Servo motor 3 that drives second fixed-capacity hydraulic pumps 1 and 2, and 4-port 3-position electromagnetic switching valve that controls hydraulic fluid from the first and second fixed-capacity hydraulic pumps 1 and 2 above 5 and a controller 6 for controlling the servo motor 3.

 [0034] The first and second fixed displacement hydraulic pumps 1 and 2 are examples of the first and second fixed displacement hydraulic pumps.

 The first fixed displacement hydraulic pump 1 has a medium capacity, and the second fixed displacement hydraulic pump 2 has a small capacity smaller than the medium capacity of the first fixed displacement hydraulic pump 1.

 The electromagnetic switching valve 5 has a first input port P1, a second input port P2, an output port A, and a return port R.

 [0037] Further, the electromagnetic switching valve 5 includes a first position SI in which the first and second input ports PI and P2 communicate with the output port A, while a return port R is closed, and the first input port. P1 communicates with output port A, while the second input port P1 communicates with return port R, second position S2, and the first input port P1 communicates with return port R, while the second input port P2 communicates with output port A. A third position S3 communicating with the output port A;

 [0038] Furthermore, the electromagnetic switching valve 5 has solenoids a and b. When the solenoids a and b are demagnetized, they are located in the neutral position, that is, the first position S1, and only the solenoid a is excited. Positioned at the second position S2 and energized with solenoid b only, it is positioned at the third position S3.

[0039] The discharge port of the first fixed displacement hydraulic pump 1 is connected to the first input port P1 of the electromagnetic switching valve 3 via the first discharge line 11, and the second fixed displacement hydraulic pump 2 This discharge port is connected to the second input port P2 of the electromagnetic switching valve 3 via the second discharge line 12. Further, the output port A of the electromagnetic switching valve 5 is connected to a load line 15, and the load line 15 communicates with a main hydraulic circuit 16. The return port R of the electromagnetic switching valve 5 is connected to the tank. A first check valve 21 is connected between the first discharge line 11 and the load line 15 so that the flow toward the load line 15 is forward. Further, a second check valve 22 is connected between the second discharge line 12 and the load line 15 so that the flow toward the load line 15 is forward. Furthermore, a relief valve 23 is connected to the load line 15.

 In addition, a pressure sensor 25 is connected to the load line 15 so that the pressure of the load line 15 is directly detected by the pressure sensor 25.

 On the other hand, the servo motor 3 is provided with a position detector 26 that also serves as an encoder for detecting the rotational position of the servo motor 3. This position detector 26 is used to indirectly detect the flow rates of the two first and second fixed displacement hydraulic pumps 1 and 2, and is an example of a flow rate detection sensor.

 [0043] Further, the controller 6 receives the output of the pressure sensor 25 and the position detector 26, and also receives the pressure command and the flow rate command, and the pressure and flow rate of the load line 15 are changed to the pressure command and flow rate. The servo motor 3 is controlled so that the pressure and flow rate correspond to the command.

 Specifically, the controller 6 includes a pressure control unit 31, a limiting unit 32, and a rotation speed control unit 33. The pressure control unit 31, the limiting unit 32, and the rotation speed control unit 33 are configured by software, hardware, and the like of a microphone computer.

 [0045] The pressure control unit 31 receives the pressure command and the pressure detection signal Pf from the pressure sensor 25, and outputs a pressure control signal Vp based on a deviation between the pressure command and the pressure detection signal Pf. Output. The pressure control unit 31 converts the pressure deviation into a pressure control signal by so-called PID (proportional / integral 'minute) control.

 [0046] The restriction unit 32 has a function similar to that of a limiter circuit, and receives the pressure control signal Vp and the flow command from the pressure control unit 31, and the pressure control signal Vp responds to the flow command. When the value is larger than the predetermined value, a restriction according to the flow rate command is added, and a restriction control signal VL corresponding to a desired rotation speed is generated and output.

[0047] Although not shown, the controller 6 determines whether the flow rate command represents a large flow rate, a medium flow rate, or a small flow rate according to a predetermined standard, and the determined large flow rate, medium flow rate. Depending on the flow rate and the small flow rate, the solenoid directional valve 5 is moved to the first, second and third positions S1 , S2, S3 outputs a control signal to solenoids a and b.

[0048] Further, the rotational speed control unit 33 is, for example, an electromagnetic switching valve determined by the number of detection signals received from the position detector 26 per unit time, that is, the rotational speed of the servo motor 3 and the control signal. The flow rate is detected based on the position SI, S2 or S3 of 5, that is, the amount of hydraulic oil supplied to the load line 15 per constant rotation angle of the servo motor 3.

[0049] Further, the rotational speed control unit 33 generates a rotational speed control signal according to the deviation between the limit control signal VL from the limit unit 32 corresponding to the desired flow rate and the detected flow rate. Output to the servo motor 3 and control the pressure and flow rate of the load line 15 so that the pressure and flow rate correspond to the pressure command and flow rate command. The rotation speed control unit 33 functions as a driver, and the rotation speed control signal is an AC motor control current.

[0050] The hydraulic driving apparatus having the above-described configuration operates as follows.

 [0051] Now, it is assumed that the low pressure and large flow rate is controlled by the pressure command and the flow rate command. At this time, the controller 6 positions the 4-port 3-position electromagnetic switching valve 5 at the first position S1.

 [0052] Then, a medium flow rate hydraulic fluid flowing from the medium capacity first fixed displacement hydraulic pump 1 to the first input port P1 of the electromagnetic switching valve 5 and a small capacity second fixed displacement hydraulic pump 2 To the second input port P2 of the electromagnetic switching valve 5 joins, and a large flow rate of fluid flows from the output port A to the load line 15.

 [0053] At this time, the controller 6 determines the load line 15 based on the pressure command indicating low pressure, the flow command indicating large flow rate, the signal from the pressure sensor 25, and the signal from the position detector 26. The rotation speed of the servo motor 3 is controlled so that the pressure and flow rate of the servo motor 3 become the low pressure and large flow rate.

 As described above, when the electromagnetic switching valve 5 is located at the first position S1, the load line 15 is controlled at a low pressure and a large flow rate.

More specifically, the pressure control signal Vp output from the pressure control unit 31 of the controller 6 and the pressure control signal Vp based on the deviation between the pressure command and the pressure detection signal is limited by the limiting unit 32 according to the flow rate command. To generate a limit control signal VL. And this limit control signal V Based on L and the flow rate calculated by the signal from the position detector 26 and the control signal representing the first position SI, the rotational speed control unit 33 determines the pressure and flow rate of the load line 15 as a pressure command. Also, a rotation speed control signal for controlling the pressure and flow rate according to the flow rate command is generated and output to the servo motor 3.

[0056] In this way, the restriction unit 32 creates a restriction control signal VL by adding the restriction according to the flow rate command to the pressure control signal Vp, and controls the pressure and flow rate based on the restriction control signal VL. Therefore, pressure control and flow rate control can be performed accurately and smoothly.

 Next, it is assumed that the medium-medium-pressure flow rate is controlled by the pressure command and the flow rate command.

At this time, the controller 6 positions the 4-port 3-position electromagnetic switching valve 5 at the second position S 2.

 [0059] Then, the medium flow rate hydraulic fluid flowing from the medium capacity first fixed displacement hydraulic pump 1 to the first input port P1 of the electromagnetic switching valve 5 is supplied from the output port A to the load line 15. On the other hand, a small flow rate of hydraulic fluid flowing from the small fixed second fixed displacement hydraulic pump 2 to the second input port P2 of the solenoid directional control valve 5 is discharged from the return port R to the tank T, and the second fixed displacement hydraulic pump Pump 2 unloads.

 [0060] At this time, the controller 6 determines the load line 1 based on the pressure command indicating the medium pressure, the flow command indicating the medium flow rate, the signal from the pressure sensor 25, and the signal from the position detector 26. The rotation speed of the servo motor 3 is controlled so that the pressure and flow rate of 5 become the above intermediate pressure and medium flow rate.

 As described above, when the electromagnetic switching valve 5 is located at the second position S2, the medium pressure flow is controlled with respect to the load line 15.

[0062] Specifically, the pressure control signal Vp output from the pressure control unit 31 of the controller 6 and the pressure control signal Vp based on the deviation between the pressure command and the pressure detection signal is limited by the limiting unit 32 according to the flow rate command. To generate a limit control signal VL. Then, based on the restriction control signal VL, the flow rate calculated by the signal from the position detector 26 and the control signal representing the second position S2, the rotational speed control unit 33 determines the pressure of the load line 15 And the flow rate to control the pressure and the medium flow and the flow rate according to the flow command. A rotation speed control signal is generated and output to servo motor 3.

[0063] In this way, the restriction unit 32 creates a restriction control signal VL by adding the restriction according to the flow rate command to the pressure control signal Vp, and controls the pressure and flow rate based on the restriction control signal VL. Therefore, pressure control and flow rate control can be performed accurately and smoothly.

 [0064] Next, it is assumed that high pressure and small flow rate are controlled by a pressure command and a flow rate command.

At this time, the controller 6 positions the 4-port 3-position electromagnetic switching valve 5 at the third position S3.

 [0066] Then, the medium flow rate hydraulic fluid flowing from the medium capacity first fixed displacement hydraulic pump 1 to the first input port P1 of the electromagnetic switching valve 5 is discharged from the return port R to the tank T, (1) While the fixed displacement hydraulic pump (1) is unloaded, the small second hydraulic (2) fixed displacement hydraulic pump (2) also receives a small amount of hydraulic fluid flowing from the output port A to the second input port P2 of the solenoid valve (5). Supplied to load line 15.

 At this time, the controller 6 loads the load line 15 based on the pressure command indicating high pressure, the flow command indicating small flow rate, the signal from the pressure sensor 25, and the signal from the position detector 26. The rotation speed of the servo motor 3 is controlled so that the pressure and flow rate of the servo motor 3 become the high pressure and small flow rate.

 [0068] As described above, when the electromagnetic switching valve 5 is located at the third position S3, the load line 15 is controlled at a high pressure and a small flow rate.

 [0069] Specifically, the pressure control signal Vp output from the pressure control unit 31 of the controller 6 and the pressure control signal Vp based on the deviation between the pressure command and the pressure detection signal is limited by the limiting unit 32 according to the flow rate command. To generate a limit control signal VL. Then, based on the restriction control signal VL, the flow rate calculated by the signal from the position detector 26 and the control signal representing the third position S3, the rotational speed control unit 33 determines the pressure of the load line 15 And a rotational speed control signal for controlling the flow rate so as to be a high pressure and a small flow rate according to the pressure command and the flow rate command, and output them to the servo motor 3.

[0070] In this way, the restriction unit 32 creates a restriction control signal VL by adding the restriction according to the flow rate command to the pressure control signal Vp, and the pressure and flow rate are determined based on the restriction control signal VL. Therefore, pressure control and flow rate control can be performed accurately and smoothly.

 [0071] In this way, the three-stage operation mode of low pressure, large flow, medium pressure, medium flow, and high pressure, small flow rate can be achieved by using only one 4-port 3-position electromagnetic switching valve 5 and the connection structure described above. By selecting and unloading and joining the two pumps as appropriate, the shaft torque required for the servo motor 3 can be reduced.

 Therefore, according to this hydraulic pressure drive device, it is possible to achieve both high pressure control and large flow rate control, and it is possible to reduce the current value required by the servo motor 3 and the controller 6. The controller 6 can be made small and inexpensive.

 [0073] Further, in the above hydraulic drive device, since the current value is small, if high pressure and small capacity control is selected, the pressure can be maintained for a long time at a high pressure.

 [0074] Next, the electromagnetic switching valve 5 is locked with, for example, dust and the like, between the first position S1 and the second position S2, or between the first position S1 and the third position S3. It is assumed that the first input port P1 or the second input port P2 and the output port A or the return port R are closed.

 [0075] At this time, the force at which the pressure in the discharge lines 11 and 12 is going to rise, the first check valve 21 and the second check valve 22 are opened, and the first and second fixed displacement hydraulic pumps 1 and 2 Is supplied to the load line 15 by bypassing the electromagnetic switching valve 5. In this way, when the electromagnetic switching valve 5 fails, the hydraulic oil bypasses the electromagnetic switching valve 5 with the first check valve 21 and the second check valve 22, thus preventing damage to piping, hydraulic equipment, etc. be able to.

 [0076] Further, when the pressure of the load line 15 is going to be excessive due to the hydraulic oil supplied from the first and second check valves 21, 22, the hydraulic oil is released to the tank T by the relief valve 23. Thus, it is possible to prevent the pressure from becoming excessive and to prevent damage to the device.

 [0077] In the above embodiment, the pressure of the load line 15 is directly detected by the pressure sensor 25, but the current value flowing through the servo motor 3 is detected by the current sensor, and the pressure is indirectly detected based on the current value. May be.

In the above embodiment, the position detector is used as an example of the flow rate detection sensor, and the force that detects the flow rate based on the rotational position and time of the servo motor 3 The rotational speed of the servo motor 3 is directly detected. Then, the flow rate may be detected. Further, the controller used in the present invention is not limited to the controller 6 of the above-described embodiment. For example, even if the controller has a difference selection unit as shown in FIG. 4 of Japanese Patent Publication No. 2000-320466. Any device that controls pressure and flow according to the pressure command and flow command can be used.

Claims

The scope of the claims  [1] Two medium-capacity first fixed-capacity hydraulic pumps (1) whose shafts are connected to each other, and a second fixed-capacity hydraulic pump (2) with a smaller capacity than the above-mentioned one When,  A first input port (P1) connected to the discharge port of the first fixed displacement hydraulic pump (1) and a second input connected to the discharge port of the second fixed displacement hydraulic pump (2) The first and second input ports having a port (P2), an output port (A) connected to the load line (15), and a return port (R) connected to the tank (T). (PI, P2) communicates with the output port (A), while the return port (R) closes to the first position (S1), and the first input port (P1) communicates with the output port (A). On the other hand, the second input port (P2) communicates with the return port (R) at the second position (S2), and the first input port (P1) communicates with the return port (R). A four-port three-position solenoid valve (5) having a third position (S3) where the input port (P2) communicates with the output port (A);  A servo motor (3) for driving the first fixed displacement hydraulic pump (1) and the second fixed displacement hydraulic pump (2);  A pressure sensor (25) for directly or indirectly detecting the pressure of the load line (15), a flow rate detecting sensor (26) for detecting the rotational position or speed of the servo motor (3), and the pressure sensor (25) And the flow rate detection sensor (26) and the pressure command and flow rate command, the pressure and flow rate of the load line (15) are adjusted to the pressure and flow rate according to the pressure command and flow rate command. The controller (6) that controls the servo motor (3)  A hydraulic drive device comprising: [2] In the hydraulic drive device according to claim 1,  Between the discharge port of the first fixed displacement hydraulic pump (1) and the first input port (P1) of the electromagnetic switching valve (5) and between the load line (15), A first check valve (21) connected so that the flow toward the load line (15) is forward, The load line is connected between the discharge port of the second fixed displacement hydraulic pump (2) and the second input port HP2) of the electromagnetic switching valve (5) and between the load line (15). Toward (15) With a second check valve (22) connected so that the flow is forward  A hydraulic drive device comprising: [3] In the hydraulic drive unit according to claim 1 or 2,  A hydraulic drive device comprising a relief valve (23) connected to the load line (15).  [4] In the hydraulic drive device according to claim 1 or 2,  The controller (6)  A pressure control unit (31) that receives the pressure command and the pressure detection signal of the pressure sensor force and outputs a pressure control signal (Vp) based on a deviation between the pressure command and the pressure detection signal; ,  In response to the pressure control signal and the flow rate command from the pressure control unit (31), the limit unit outputs a limit control signal (VL) generated by adding a limit according to the flow rate command to the pressure control signal ( 32) and  Based on the restriction control signal from the restriction part (32) and the flow rate detection signal from the flow rate detection sensor (26), the pressure and flow rate of the load line (15) are changed to the pressure command and flow rate command. A rotation speed control unit (33) for generating a rotation speed control signal for controlling the pressure and flow rate according to the pressure and outputting it to the servo motor (3);  A hydraulic drive device comprising: